Hail Damaged Roof Replacement: Part 10 – Dormer Roof Flashing

The dormer roof flashing details are shown including the stucco step flashing, apron flashing (headwall flashing) and counter flashing installation steps. A section of rotted fascia board is repaired with PVC composite trim board. This project is continued from Hail Damaged Roof Replacement – Part 9.

Original Dormer Roof Caulk

This is the old hail damaged roof with a closeup of the dormer with stucco siding. I’m not sure if the thick line of caulk was an original part of the roof or added later to prevent a leak.

Old Roof and Stucco Dormers

A caulk job like this at the roof-to-wall intersection just doesn’t seem quite right.

Closeup of the Caulk at the Dormer Roof to Wall Junction

When the old roof shingles and felt were torn off, the roofers discovered there wasn’t any flashing under the shingles along the front of the dormer! Hence the odd looking caulk job to seal between the stucco wall and shingles.

New Dormer Roof Installation

The old asphalt shingle roof has been torn off. The gray color GAF StormGuard® leak barrier (ice and water shield) has been installed in the roof valleys, followed by the GAF Shingle-Mate® fiberglass reinforced roofing felt (equivalent to 30 lb felt). The drip edge flashing is being installed on the far left dormer, too.

New Roof Installation: Dormer Roof and Front Gable

I was really impressed with the roofing crew’s care and attention to detail. A section of plywood is notched for the laddervator rails and nailed to the dormer to make a stand-off to protect the dormer drip edge flashing. The rotted fascia board end where it wicked up moisture from being in contact with the roof is highlighted in the red square. The old step flashing is left in place along the sides of the dormers because removing the old step flashing would damage the stucco.

New Roof Installation: Dormers with Stucco Siding

Dormer Rotted Fascia Repair

I bought a 1in x 8in x 10ft AZEK PVC trim board at Home Depot. The AZEK PVC trim board is waterproof, rot proof and insect proof. I asked the roofing crew if they would pull off the rotted trim board and install the new AZEK fascia board if I sawed and mitered the new board with my Dewalt compound miter saw. The roofing crew agreed as it was a small job and had I won their goodwill by loading up the freezer with 24 packs of bottled water that I handed to them throughout the hot days.

This is the rotted wood fascia board with the AZEK PVC trim board:

Rotted Fascia Repair: AZEK 1″ x 8″ PVC Trim Board

The new AZEK 1″ x 8″ PVC fascia trim board being installed:

AZEK PVC Fascia Board Installation (1″ x 8″)

Dormer Roof Corner Flashing & Step Flashing Installation

Two pieces of galvanized roll flashing and bent and cut with tin snips to start the flashing at the outside corner of the dormer: 1) A flat section is slipped under the stucco and extends to the left under the original step flashing (not visible here); 2) A starter piece of step flashing with a rounded kickout extends to the left under the shingles.

Dormer Roof Corner and Step Flashing Detail

Lifting a shingle, the starter piece of galvanized corner flashing with a kickout extends under the shingle:

Stucco Dormer: Roof Corner Step Flashing

This photo of the outside corner flashing opposite the dormer provides a clearer view of the roof flashing installation technique:

Roof Corner Flashing and Kickout Step Flashing

A section of apron flashing (also called headwall flashing) is cut from galvanized flashing stock and installed at the front of the dormer to cover the roof-to-wall joint. The apron flashing lays on top of the shingles to shed water. The ends of the apron flashing extend under the step flashing with kickouts at the corners of the dormer.

Dormer Roof-to-Wall Apron Flashing

View of both dormers and apron flashing installation progress:

Dormer Roof Apron Flashing and Step Flashing Kickouts

Black counter flashing is installed over the step flashing and apron flashing with hammer drive anchors set in the stucco. The counter flashing is caulked with BASF Sonolastic® NP 1™ to make a watertight seal against the stucco wall. Notice the red arrow where a section of galvanized kickout flashing is installed behind fascia board to keep water away from the plywood soffit.

Stucco Dormer Roof Counter Flashing Installation

The hammer drive anchors and exposed nail heads in the apron flashing are sealed with NP1:

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2 Comments

Hi Bob – having hail restoration performed on my roof now. 2 quick questions – 1) noticed that you have now installed shingle over ridge vent on the dormer ridges. However, I don’t see any way for air to get into the soffit area (i.e. 3″ circle vents, soffit vent strips or drip edge vent). How will the ridge vent function (let hot air out) if there’s no way for cool air to get in allowing the natural “heat rises” process to take place. 2) I noticed on your low sloped porch roof that the roofers installed the GAF Shingle Mate felt FIRST directly to the plywood AND THEN installed the ice shield over top of it. So that water can’t back up or be blown under the leading edge/first course of plywood, shouldn’t the first course of ice shield have been put down first and then the felt overlapped 4″ over the headlap? By the way, thank you very, very much for creating this absolutely incredible, highly detailed and easy for a layman to understand, time consuming, educational “How to” segment. I know this must have taken you 20+ hours to put together!!

Soffit vents should be installed at the dormers. I’ll get around to it someday. The advantage of ridge vents even without soffit vents here is the dormers were originally completely sealed. Ridge vents alone allow for moisture equalization.

Ice & water shield: Roofing felt under the GAF Stormguard membrane isn’t necessary on the main roof deck. I’d have to ask the roofers but it may be simply the materials were spec’d for the entire roof. I imagine roofing felt under the membrane will make reroofing easier because the sticky membrane will otherwise meld itself to wood roof deck.

> so that water can’t back up or be blown under the leading edge/first course of plywood That would be better especially in a hurricane prone area. Roofing felt was laid over the drip edge flashing along the horizontal roof edges, however the flashing overlaps the felt along the rakes.

> I know this must have taken you 20+ hours to put together!! More like 100 hours for the entire series! There’s a reason why I don’t have time to watch TV.